Synchronizing signal generator



6 Sheets-Sheet 1 Filed July 30, 1942 Kvm. Re...

NQQI- Y msm Wmskkk b kNOmTV ATTORNEY June 6, 944- v K. scHLEslNGER2,350,536

SYNCHRONIZING SIGNAL GENERATOR Filed July 50, 19442 A 6 Sheets-511881l 2"'F (a) IIII all E y I/l 1 1 e 875// (9,) 6e) S e?) U A j lNvENToRT'TORNEY K. SCHLESINGER 2,350,536

SYNCHRONIZING SIGNAL GENERATOR `Fume 6, i944.

6 Shee'ts-Sheet 5 Filed July 30, 1942 INENo `A'TTORNEY June 6, 1944. v KSCHH-:SINGER 2,350,536

SYNCHRONIZING SIGNAL GENERATOR ATTRNEY June 6, 1944- K. scHLEslNGERSYNCHRONIZING SIGNAL GENERATOR Filed July so, 1942 mwa.

6 Sheets-Sheet 6 INVENOR my ATTORNEY Patented June 6, 1944 SYNCHRONIZINGSIGNAL GENERATO Kurt Schlesinger, West Lafayette, Ind., assignor toRadio Corporation oi' America, a corporation of Delaware ApplicationJuly 30, 1942, Serial No. 452,921

(Cl. Uil-69.5)

8 Claims.

This invention is directed to television systems, and particularly to amethod and means for producing synchronizing signals (hereinafter termedsync signals because of usage in the art).

Further, the invention is directed to systems wherein the produced syncsignals shall be in accordance with standards proposed by the FederalCommunications Commission and reported ln its Docket 5806, dated May 3,1941.

In the prior art, sync signal generators have been developed and usedsuccessfully. Such apparatus has been proposed in'various forms, and one,form which has been used, to some extent, is that disclosed in briefform in Principles of Television Engineering by D. G. Fink, published byMcGraw-Hill Book Company, Inc., New York, 1940, and particular referenceis made to that portion of the publication referred to which commenceson page 402, under the title Synchronizing Signal Generator, and whichcontinues through page 414.

In the prior art arrangements for instance, the sync signal generatorincluded, mainly, two units, of which one was generally designated asthe timing unit and the other was designated as the shaping unit. Thetiming unit is usually interlocked with a power supply frequency andserves to control the second unit which, as before stated, is known'asthe wave shaping unit. These various units are described in some detailin the publication hereinabove referred to, and, when in operation,serve to provide a synchronizing signal wave form of the generalcharacter hereinafter disclosed by Fig. l of the drawings which will bedescribed in what is to follow;

The wave form for controlling television image reproduction generallycomprises horizontal synchronizing pulses which, after a predeterminedtime, are followed by certain equalizing pulses. The equalizing pulsesare six in number and occur at twice the line frequency, or, in otherwords, at twice the frequency of the horizontal synchronizing pulses.Following the six equalizlng pulses there are produced verticalsynchronizing pulses over a period of time corresponding to the timerequired to produce three'lines of picture transmission. The verticalsynchronizing pulses are each slotted, so there' result, in effect, sixseparate slotted pulses. These vertical impulses are then followed bysix additional equalizing pulses occurring at double line frequencywhich,-

' are a certain predetermined nm Following the second groupoiequalizinpulses v y '.,imtitg the first of the equalizingfpulsesraboverefered toagain occurs, which, asis'evidentgwilljbe'at the time of completingeachsucceedingjpicture field transmission. i

According to the proposedfst VHclardsl for mission, vertical blanking inrvthe'picture` :sfintended to take place during theperiod offtransmission of all of thevrst' grou'pfv ofl ,equalizing pulses, thegroup of vertical synchronizingpulses,

' the second group of equalizing pulses, and acertain portion of thesucceeding group of horizontal The .Yerial' blkig period may thus beassumed to"includeL a period of time (according to proposed standards)corresponding to.0.075 Vi0l005 V,','where-Vjrepref sents the time fromthe start of one picture' eld to the start of the next succeedingpicture eld'.

According to the present invention, it.i spr`o posed to develop, withapparatus `of asubsta'n- Y tially simplied nature, synchronizing signalsof the general form hereinabove describedjand known in the art, and tothifsend, provisionis made for accomplishing-y `the 'results' bym purely4electronic means of simplified hating, y

1t is an object'of the` presentmvenuon1-tb pi; vide a system forproducing television synchro,-

Anizing signal wave forms particularly adaptable for amplitudemodulationoi' the video intelligence which conform completely topresently .existing standards. f 1

Another object of the invention/is to provide for developing signals ofthe aforesaid'character by means of purely electronicappafatus. v .g

Still another object of the 'invention toprovide a system for developingsynchronizing sig,- nals where all of the signals arelderived 'from oneand the same master` oscillator which is preferably a non-sinusoidalpulse generator ofA pre-l distorted waveform.

Another object is to provide for generating sig,- nals of the abovecharacter ,with apparatus which overcomes one or more known and existingl ,disjadvantages and defectsof the'prior ,artarrangements. For example,the relativephaseshift of signal is made invariable `withthepresentjapparatus, and all groups of signals havle'the same leadingedgein common. g A further object of the invention is to provide anddevelop a system rwherein n the j number of 2.tubesrequiredtogeneratethedesiredfrmof munmbstanuauy reduced.

Still a further obiect is that of developing a system vfor generatingsinals of the aforesaid signal generator which'occupies a relativelysmall space because ofthe reduced number of tubes and other componentparts to provide a system for developingsignals of the aforesaidcharacter which is easily serviced and maintained in satisfactory stableoperation. and a system which is relatively simple in its arrangementand construction.

Other and further objects and advantages naturally will becomeapparentto those skilled in the art from a reading of the followingspecification in connection with the accompanying drawings, whei'ein-lFig. 1 is a diagrammatic representation of the general form ofsynchronizing signal now considered as standard:

Fig. 2 is a schematic representation of certain wave forms serving toillustrate the general principles of operation of the herein to bedescribed device;

Fig. 3 is a schematic block diagram of the circuit instrumentalitiesherein to be disclosed:

Fig. 4 is a diagrammatic representation of certain wave forms occurringin the apparatus diagrammatically represented by Fig. 3

Fig. 5 is a series of curves relating particularly to theoperation 'ofthe single pulse relay schematically disclosed as a part of Fig. 3 andmore particularly set forth by Fig. 6; and,

Fig. 6 is a schematic diagram of one form of the complete circuitinstrumentality diagrammatically represented in block form by Fig. 3.

Referring now to the drawings for a further understanding of theinvention, the system in general is based upon an arrangement whereinthe various groupsof sync signals, namely, the line pulses, theequalizing pulses and the frame pulses (commonly referred to as L. E.F.) as well as the blanking signals, are derived from one and the samemaster oscillator by relatively simple clipping devices to whichvariable biases are applied. 'Ihe master oscillator generates pulseenergy of a predetermined non-sinusoidal wave form in which the durationis made equal to that desired for the equalizing pulses and therepetition rate is twice the line frequency. For leach oscillatory cyclethe energy is first negative and then positive with cessation ofoperation after the negative and positive pulses for approximately '76%of the cycle. s

Such a system, as will herein be described in more detail, oers animportant advantage in that the relative phase relation is' invariableat al1 times, and all signal groups have the same leading edge incommon, sc that the phase relationship between all groups of signals isalways fixed and correct.

the input and the output signals is subject to variance to some extent.Therefore, the present would be subject to shift in a somewhat erraticmanner with reference to the line signals, but, by making provisions sothat the output signal is taken as a sort of potential impulse, for instance, a highly precise timing signal may be obtained by using theimpulse from the master oscillator to control the final signalproduction.

It will be apparent from the showing of Fig. l that the televisionsynchronizing wave form., as it has now been approved by the Commission,comprises recurring line synchronizing impulses I which occur with theirleading edges spaced with a time separation H (one picture line period).At the bottom of each picture field transmitted, a series of sixequalizlng pulses 3 are initiated. These equalizing impulses are each ofthe same amplitude as the line synchronizing impulses, so that intransmission they represent, as do the line synchronizing impulses,substantially 100% modulation of the carrier. However, the equalizingimpulses are of less width and less duration than the line synchronizingimpulses, and, according to the adopted standards, the area is permittedto vary between 0.45 and 0.5 of the area of each horizontal or linesynchronizing impulse. After the series of six equalizing pulses aredeveloped these are followed by the vertical synchronizing impulses 5,which are slotted as shown at 1.

The time period indicated between the beginning of one verticalsynchronizing impulse and the beginning of the next succeeding verticalsynchronizing impulse is 0.5 times the time between any two successiveline synchronizing impulses. I-'he width of the slotted portion of thevertical synchronizing impulse is to be equal to approximately 0.07K,where H is the time from the start of one line synchronizing pulse tothe start of According to some prior art systems, frequency y entirely,because the phase relationship between the next line synchronizingpulse, so that it be comes evident that the width of each verticalsynchronizing pulse is approximately 0.43H.

After the succession of six vertical synchronizing pulses 5 has beenproduced within the time period represented by three times the timeexpiring between the beginning of one line synchronizing impulse and thebeginning of the next succeeding line synchronizing impulse, a secondseries of equalizing pulses 3', also six in number, is developed, andthese equalizing pulses then are followed by the normal linesynchronizing impulses 0.

The time period between the start of the first equalizing impulse of theilrst group and the commenment of the next succeeding transmission ofvideo signals represented conventionally at il, is made equalsubstantially to 0.075 V, where V represents the time from the start ofone picture ileid to the start of the next picture field, and, accordingto the illustrated wave form, it will be seen that eight horizontalsynchronizing pulses follow the second group of six equalizing pulsesprior to the commencement of the4 transmission of video signals,represented at ii, for the top of the next picture field.

As shown, each horizontal synchronizing Pulse, each equalizing pulse andeach vertical pulse is maintained vat substantially 25% greater carriervoltage than any video signal Il, as is customary in any system whereinnegative modulation" is Provided, by which is meant that white of resentsubstantially 100% modulation of the carrier, and consequentlyproducesignalsfwhich can be describedv as being "blacker than theblackest z black.

With the foregoing thoughts in mind, reference may be made to Fig. 2 oi'the drawings, and first to curve a thereof. By this curve, as inall'others, the ordinates represent amplitude and the abscissaerepresent time. By referring to curve a of Fig. 2, it will be seen Ithatthis curve represents generally the wave form I5 of the masteroscillator which develops output pulse -energy at a frequency of 31,500cycles per second (assuming a 525 line television picture as will beherein assumed for illustrative purposes). Thus, lthe elapsed timebetween any two peaks of the output energy is represented as I/mosecond, and the width of the pulse in the negative direction (to formthe slots in the vertical sync) is represented as 8% H, where again H,as in Fig. l, represents the time elapsed between the starting of oneline andthe starting of the next succeeding line, while the width in thepositive direction (to develop the equalizing pulses) is 4% H.

It can be seen from the showing of curve a.of Fig. 2 that the masterwave thus developed is a sequence of pulses occurring in the desiredwidth and at the desired frequency and starting with a peak in thenegative direction. Each wave trace, comprising'the negative and thepositive half, has a' combined period of 12% of the repetition period ofeach line, with the'duration of either the positive portion of the pulseamounting to 4% of the line frequency, which line frequency may bederived from the master frequency by a frequency reduction of the orderof.1:2. The 4% width is intended to be the duration ofi the equalizingpulses to occur between the line synchronizing pulses and the verticalsynchronizing pulses, as was' hereinabove explained, in accordance withthe standards of the RMA and those recommended by the FederalCommunications Commission, all as above stated.

In curve a of Fig. 2, one clipping level, above the zero reference line`O, inthe positive direction has been indicated by the legend E, fromwhich the equalizing pulses will be derived, and` a second clippinglevel has been indicated as spaced from the zero reference line O by adistance represented by F from which the frame synchronizing signals areto be derived. There thus results from clipping the master wave at thelevel E, a series of pulses such as those shown, for instance, by curveb of Fig. 2, which appear as a series of pulses l1 each spaced in time,one from the other, by $51,500 second, and for a resultant signalresulting from clipping, at the level F, a signal such as that shownshematically by curve c of Fig. 2 is found to be developed. This seriesof signals will be those' resulting from clipping below the zero line ofcurve a, andconsethe start of each succeeding line of synchroniz-L1 ingimpulses and the interruption periods designated by the recesses 2|provide signal interruptions existing ior 8% of the line period, asshown by curve a. and which thus correspond to the periods ofinterruption in the vertical sync pulse interval 1, as shown by Fig. l.l

It can be seen further, from what has-been above stated, that theleading edge of both the lequalizing pulses I1v and the .frame signalsI9 are coincident in time. The line and the blanking signals arederivedfrom the ysame master wave by frequency halving after the masterwave is inverted, as shown by curve d of Fig. 2.

Let -it now be assumed that the frequency halver responds to a positivepeak and is given an exponential output wave shape by a capacityloading. The wave form may be considered to be as shown by curve e ofFig. 2. In this case, the blanking and super sync pulses may be derivedfrom the output, again by two clipping procedures indicated by clippingat the levels S and B representing, respectively, the 'clipping levelsfor the high level super sync signals and low level blanking signals.The S level clipping may easily be placed at such a voltage that theleading edge of the resultant sync pulse becomes coincident with theleading edge of the equalizers and frame signals, as is shown, forinstance, by

blanking signals conventionally Ashown at 21.

Reference may now be made to Fig. 3 of the drawings which is a schematicrepresentation of the general arrangement of the various tube circuits,which, in co-operative relationship, produce the various clipping andwave shaping effects schematically represented in Fig. 2 abovediscussed. In connection with a consideration of the diagrammaticrepresentation of Fig. 3, reference should also be-had to Fig. 4,wherein various wave shapes appearing in the different instrumentalitiesdiagrammatically represented in Fig.

3, are indicated. By the various portions of Fig.

4, the letters indicate the wave shapes at the points where -the letterindications appear in Referring now to Fig. 3, the master oscillator 3|is provided for developing pulse energy of a wave form shown, forinstance, by the waves of Fig. 2a or Fig. 4a. These pulses are generatedas was indicated, to be repeated at a frequency of 31,500 cycles persecond (assuming herein, as-

` above stated, that the system disclosed is operatvelapsed time beingwith a `525 line television picture, although it is perfectly evidentthat the same circuits are applicable to systems using a differentnumber of picture lines and a different number of picture frames andfields than the assumed 30 and 60 respectively). It was above noted alsothat the wave should be inverted to produce some of the effectsnecessary. l

, It has accordingly been provided so that the master oscillator 3| isthe source from which three separate signals are derived. To providethis effect, the output from the master oscillator Such' pulses arerepresented schematically by the,

issupplied (nrstlto acathode follower' or buffer stage Il: (second) tosupplyfan inverted output wave such as that .shown by Fig. 2d orl'ig. 4bto the line oscillator Il and a frequency divider I'I, and (lastly) tocontrol a super sync mixer ll witha wave form such as shown in Fig. 2a.The cathode follower or buifer stage 3l feeds its output, in turn. to aseries of frequency dividers Il, 4I, and Il respectively, each of whichis driven from the preceding oscillator, and the cathode follower orbuifer stage acts to prevent any possible load variations in thefrequency divider stages from being introduced upon the masteroscillatorIl by the controlled frequency reducing system.

'111e line oscillator Il is adapted to generate output energy at afrequencywhich is half that of the master oscillator ll, and,accordingly, the

output pulses therefrom occurat a rate of 15,750 cycles per second.Along with the line frequency oscillator ll, the inverted energy fromthe master oscillator 3l is applied also to a frequency divider unit 31which operates to develop an outmaticfrequencycontrolactionmustbecarriedout. Accordingly. l portion of the output yenergy from the lastfrequency divider Il is appiiedtov, an automatic frequency control unit4l. ."lfhe wave form output from the last frequency divider of the grouphas, as indicated. a generally quasi-linear shape as derived from thelast stage quasi-linear form of 4d--and then fed back by oscillator,or.5,250 cycles, which is keyed for the duration of the frame pulses.Finally, the master oscillator also feeds its nonlnverted output wave,such as that shown by Fig. 2a or Fig. 4a, to the super sync mixer ll,wherein wave formations corresponding to waves e, f and g of Fig. 2' aredeveloped by suitable clipping actions'. 1

As was above stated, the master oscillator generstes its wave output,such as that shown by Fig. 2a or 4a, so that it starts with a negativepeak. From the cathode follower or buffer stage 33, a series of positivepulses, at double line frequency, as shown by the pulses of wave formFig. 4, curve c, are developed, and these pulses are thensupplied to thefirst frequency divider 4I. Essentially, the frequency .dividers Il, 42,Il and Il are blocking oscillators, the circuits of which will be moreparticularly appreciated from the showing of Fig. 6. Each of theblocking oscillators or frequency dividers 4I, I2, I3 and Il isinterlocked so as to give a resultant frequency division or reduction of525 to l. Accordingly, the output from the first frequency divider Ilappears at t/s the frequency of the master oscillator 3l, or at 10,500cycles. The output from the second frequency divider I2 is V; thelfrequency of the output of the iirst frequency divider 4i, or 1115 thefrequency of the master oscillator Il, and consequently is developed at2,100 cycles. Similarly, the frequency divider 43 reduces the outputfrequency `of the frequency divider 42 by y', and thus is 1/15 thefrequency of the master oscillator 3|, or 420 cycles. Lastly, thefrequency divider 44 reduces the output frequency of the frequencydivider by 1/1. so that its output frequency is 1,625 of higherfrequencies becauseot slightly greater stability and simplicity ofreduction.

It is evident, from what has heretofore been known in the art relatingto frequency dividers and sync signal generators, that the last stage 44of the frequency divider group is supposed to develop output energyprecisely at the ileld frequency oi 60 cycles per second. But, to obtainthis frequency accurately, a certain autoway of aconductor such as Il tothe master oscillator 3l, so as to control its frequency and maintain itat exactly 31,500 cycles per second, which is 525 x 60.

It will be apparent, from the showing of Fig.1, that the linesynchronizing impulses are to be produced continually except for theduration of nine line periods which correspond to the period of timerequired to produce and transmit the first series oi' equalizing pulses,the vertical sync pulse interval and the second series of equalizingpulses. Accordingly. it is apparent that the inverted output of themaster oscillator Il may be fed into two separate devices, namely, theline frequency oscillator Il which operates continuously at one-half thefrequency of the master oscillator (that is a frequency of 15,750cycles) and is synchronized by it through the energy supplied by way ofconductor Il. Also, the lso-called frequency divider or start-stopsystem 31, which contains the frequency divider operating at V6 thefrequency of the master oscillator 3|, is energized from and controlledby the master oscillator 3i by way of energy supplied by conductor 52.Tire output energy from the frequency divided 31 is in a step-down ratio1:6 with a pulse outputof 5,250 cycles. corresponding to a durationperiod of three times the time interval between successive linesynchronizing pulses. o'r. in other words, a time duration 3H.

The frequency divider or start-stop system 31. however, does not operatecontinuously, but is brought into action only during the picture retracemoment, and for this purpose the frequency divider unit 31 is keyed bythe output of the frequency divider unit 44 which is developing the 60cycle output, as shown by wave d of Fig. 4, and this 60 cycle energy isf ed to the frequency divider 31 by way of conductor 53. The energy fedto the frequency divider unit 31 by way of conductor 53 is of thegeneral wave form corresponding to, curve f, Fig. 4, and it will benoted, fol-instance. that this keying signal is slightly longer thanthat actually required and consequently it only serves to actuate thefrequency divider at 5,250 cycles, but cannot be used for correct timingor switching action from the line to the frame signals and back again.

In the output of' the frequency divider 31 the wave form, as shown bycurve o of Fig. 4, appears in the conductor l5 which feeds the energyvoutput'from the unit l1 into the square wave these four pulses whichare used vto trigger the square wave generator 51, whose output is shownby the curve h of Fig. 4 and appears to be a square wave voltage whichis symmetrically arranged above and below the axis and starts withnegative polarity. Special precaution is taken that this polarity isalways the same, that is to say, the square wave generator 51 must bedesigned so that it is of a type which might be callednon-communicative. This voltage then is used to serve as a bias for themaster oscillations (as per curve a of Fig. 4) which are supplied by wayof conductor 58, and consequently the two voltages represented by curvesa and h. of Fig. 4 are summed up and applied to the super sync mixer 39.

From what is to follow in the description of Fig. 6, it will be seenthat these two superimposed voltages are fed into one of the twopentodes which are in co-opgration in the super sync mixer 39 and areused to feed the line signals and the equalizing and the frame signalsinto the same output line.

To obtain this mixing action, a special relay unit 59 is provided. Thisrelay unit 59 is supplied with energy by way of conductor 6| from thesquare wave generator 51, and its purpose is that of generating aone-signal pulse of either positive or negative polarity which 'will beof' a duration corresponding exactly to a period of 9H, that is, aperiod of nine line sync pulses. The single pulse relay 59 is shown inmore detail in Fig. 5, and further reference will be made to it, but atthis time it should be borne in mind that the single pulse relay 59 is,as above mentioned, of the class termed non-communicative, that is tosay, its pulses are required to have a definite polarity.

The output 'energy from the single pulse relay 59 is shown in wave formk of Fig. 4, and the relay itself is triggered by wave energy which isrepresented by the curve f, also of Fig. 4. 'Ihis .wave form energy isderived from the square Wave generator 51 by diierentiation and,accordingly, the curve :i consists of a sequence of four separate pulsesalternating in polarity and each of very short duration, which areseparated from each other by a time period represented by 3H.Accordingly, the pulses have an altering polarity sequence of plus andminus.

In order to provide the desired type of signal, the single pulse relay59 has an inherent quality, as will be appreciated from a furtherconsideration of Fig. later to be discussed in detail, of standing by inan attending or waiting position or state until the rst positive pulseof Wave i arrives. The relay then respondsy to this one pulse but doesnot cease operation or fall back until the second negative pulsearrives, and, for the purpose of maintaining 'a state of operation ofthis character, electrical inertia ls introi duced into the circuit ofthe relay in a manner which will be described particularly in connectionwith the specic description of Fig. 5.

By the co-operative relationship of the square wave generator and thesingle pulse relay 59, the super sync mixer 39 produces, at its output,the desired succession of super sync signals which may be impressed upona predetermined type of transmission line 60, for example, a 10,000 ohmline, but the wave fronts of these resulting signals are generally notsuiciently steep to provide the exact desired signal form. To improvethe wave form, a wave shaping amplifier 5l is provided between thetransmission line 60 and the output terminals 62 and 63.

Essentially. as will be seen from the description of Fig. 6, thisshaping amplier includes. primarily, tubes of the pentode class whichare particularly capable of re-shaping the wave' as desired.Fundamentally, the purpose of the shaping amplii'ler 6| is to increasethe steepness of the leading and trailing edges to a predeterminedprecision of timing which will correspond to somewhat less than threepicture elements.

(according to RMA standards). At the same time, the amplifier 6I acts asan amplitude clipper, as well as a power amplier. As a result,approximately a 50 volt pulse amplitude is obtainable in either thepositive or the negative direction across a load connected to theterminals 62 and 63 which may be of 1,000 ohms or less. wherein alloutput signals have substantially equal height and equal slope. Thisgeneral result its pictorially represented by the curve m in Fig.

For the purpose of obtaining the blanking pulses according to thestandards pictorially represented by Fig. 1, certain additional tubesand elements are provided. To this end, there is required an additionalwave shaping amplier 85 which is of substantially like nature to thewave shaping amplier 6l' for the purpose of shaping the super syncsignals and giving the same output power and voltage. A mixing of theline and frame blanking signals is obtained in a blanking mixer 61,which preferably comprises but a single pentode connected inco-operative relationship with the suppressor grid of one of the'ampliertubes of the shaping amplier 85.

The blanking mixer 61 acts generally as an amplitude clipper and itreceives an input signal a time period equal to the duration of oneequalizer pulse or a time period of, say 0.08H.

To provide the proper length of the frame blanking signal and to operatethe mixer unit 61. another single pulse relay 69 is provided. This relay69 is adjusted to give an output pulse of exactly 12H, see curve n ofFig. 4, to provide for the picture retrace blanking, and the leadingedge of this pulse is (intended to be coincident with the leading edgeof the rst of the equalizers in the super sync. For this purpose, therelay 69 is triggered by the same series of pulses that control therelay 59, which are represented by curve i of Fig. 4, and, as Waslhereinabove stated, this wave is derived from the square wave generator51 by electrical differentiation. Means next are provided to superimposea 10% fraction of the super sync signals upon the blanking signals, andthus the transmitters may be modulated over a single channel. The outputfrom the wave shaping unit 65, as shown for instance by -curve p of Fig.4, appears at the terminal points 1l and 12.

Reference now may be made to Fig. 6 of the drawings which is a schematiccircuit diagram of a complete sync signal generator. As was outlined inreference to Fig. 3, the various tube elements shown in the circuitarrangement ot Fig. 6, have their counterparts in the schematicrepresentations. For the purpose lof enabling the tube units readily tobe identified in Fig. 6 and compared with the schematic representationsof Fig. 3, it will be seen that the combination' of the masteroscillator 3| and the buffer stage 33 is provided by the tube A and itsassociated circuit elements.

The frequency dividers 4|, 42 and 43 are provided by the blockingoscillator tubes and circuits, generally designated B, C and D. Tube Eand its circuit elements co-operate to provide thev 60 cycle stage andthe frame key signal generator. The automatic frequency control,schematically designated by the unit 45 on Fig. 3, is provided by thetube F and its circuit elements. The line frequency oscillator 35, whichis maintained in a state of continuous oscillation, is provided by thetube G and its associated circuit elements. The frequency divider 31,which pro-- vides output energy of one-sixth the frequency of the masteroscillator, is shown by the tube H and its circuit elements, with thekeying action thereon being provided by the tube and circuit E. Tubes Iand J and their circuits together represent the square wave generator,generally designated in Fig. 3 as the element 51.

The single pulse relay for developing energy pulses of the duration 9His schematically represented in Fig. 3 where the element 59 is shown ascomprising the tube K and its associated circuit elements. The tube Pand its associated circuit elements provides the single pulse relaycorresponding to the element 69 of Fig. 3, and is for the purpose ofdeveloping the pulses such as shown by curve n of Fig. 4 and which areof a duration |2H. 'I'he tubes L and M co-operate with their circuit'elements to provide the mixer stages for the super sync, such as shownby the conventional representation 39 in Fig. 3.

From the description to follow, it will be seen that the tube L and itscircuit elements develops the equalizer and frame pulses, while the tubeM develops the line pulses, and both of these tubes are keyed, in turn,by the single pulse relay K. The tube N with its circuit elements formsthe slope shaping amplier, such as the amplifier 6| of Fig. 3, while thetube O and its circuit elements provides the super sync output stage.

The blanking mixer 61 of Fig. 3 is represented f by the tube Q and itscircuit elements in Fig. 6, and the tube R, together with theco-operating circuit elements, finds its counterpart in the shapingamplifier 65 of Fig. 3. The tube S functions as the output blankingstage. 'I 'he tube T functions merely as a rectifier in the power supplyline, and the other two illustrated tubes X and Y, in Fig. 6, comprisemerely two voltage regulating lamps in the power supply chain.

Now making reference more particularly to the specific circuit of whichthat disclosed by Fig. 6 represents one form which has been foundsuitable in its function for the described purpose, it will be seen thatthe master oscillator A comprises a twin triode tube 15, which, forillustrative purposes, may be a tube of the general type known as the6F8. The first portion of this tube, comprising the cathode 11,thecontrol electrode 18 and the anode 19, is connected as a blockingoscillator with the tuned plate circuit. The interruption period isprovided by a tuned circuit comprising the condenser 8| in series withresistance elements 83 and 85, of which the resistor 83 is (wheredesired) made variable and thus is capable of providing the necessarytuning. A coupling between the plate circuit and. the grid circuit ofthe rst section of the tube is provided by way of the primary andsecondary windings of the transformer 81, as indicated.

In order to provide for changing the pulse width, for reasonshereinafter to be more fully explained, an additional capacitor 38 isprovided and connects to ground at 9|. Also connected between thecathode 11 and ground |41 is a cathode resistor 80, preferably of thevariable type, which is, in turn, shunted by a condenser 84.V Thecathode resistor 80, it will be seen, may furnish a convenient means toobtain a rather delicate adjustment of the frequency control in contrastto the more or less coarse adjustment which would be experienced by avariation of the grid leak resistor 83, but which is, of course,entirely practical.

Considering the general arrangement of the oscillator comprising the rsthalf of the tube 15 or the tube A, the coupling transformer 81 has arelatively low stray capacity, so that its natural frequency isgenerally high, which means a distributed winding should be used; and,on the other hand, the grid leak condenser 8| is of relatively highvalue. Under these conditions, it can be seen that as the circuit startsto oscillate, it acts somewhat as if the grid coil were tuned by thegrid condenser 8|, and the grid cathode resistance then becomessubstantially negligible for the positive half of the cycle. For thenegative half cycle, however, the loading effect of the grid condenser8| through the tube section comprising the cathode 11, the grid 18 andthe anode 89, substantially disappears and the period is greatly reducedsubstantially to the i natural period of the coils, which may beadjusted, furthermore, by the small capacitor 88. It is thus apparentthat the output of the blocking oscillator section of the tube 15 is awave of the general character shown by curves a of each of Figs. 2 and4, and this may be of the order of approximately 200 volts peak, asindicated.

For the purpose of lengthening the slot width in the vertical signal(that is to provide the 0.08K slot width) it can be appreciated that byeliminating the tuning of the plate coil of the transformer 81 of themaster oscillator and increasing the blocking condenser 8|, whiledecreasing or shunting grid and cathode limiters 83 and 80, the width ofthe pulse can be made wider, for example, without in en y way departingfrom the disclosure of the present invention, but by eliminating thetuning provided by the condenser 89 and the resistor 90, which was madesmall enough to give the plate circuit of the iirst half of the tube 15a generally oscillatory character, the outputl characteristic may bemodied. Of course, in this connection also it is desirable to eliminatethe tuning of the grid coil.

If, now, it be assumed that the distributed capacity across the plateand grid coils of the transformer 81 is represented by a value Cz, andthis value is substantially negligible, then it becomes immediatelyapparent that the output pulse energy from the blocking oscillator 15 isof the general wave form shown by the curve a of Fig. 2, except that thefirst negative portion of the cycle is wider than the positive portionof the cycle. The grid and the plate voltage are equal in amplitude andopposite in polarity and, accordingly, the flrsthalf period is madelonger than the second half period so that the width of the lowerportion of the pulse from the blockfactories y and 89, functioningrespectively as the line freing oscillator then becomes of a value suchthat the slots 1 (Fig. 1) are obtained by clipping at level F. At thesame time, the narrower pulse shown by the designation 0.04H of Fig. 2.curve a, for instance, which represents the equalizing pulse, isattained by the leading and trailing edges of both pulses in combinationwith`the condition of coincidence, hereinabove explained, when clippingat level E.

This condition of operation is explainable by considering that the gridcoil of the transformer i81 is connected in parallel with the blockingcondenser 8| through the grid to cathode path 18 and 11. during thefirst or positive cycle of the grid swing. As the cycle reverses,however, this path in the tube becomes non-conducting and the coil isleft alone with its distributed capacity hereinabove assumed as Cz whichis divided equally between the plate coil and the grid coil as the load.Obviously, the natural period of ,the circuit in the rst condition isbound to be longer than the period of the succeeding cycle, andconsequently the length of the slot pulse, as shown by curve c of Fig. 2can readily be changed within predetermined limiting values with regardto the desired width 0.08H by changing the value of the capacity whilethe repetition frequency of all the pulses can readily. be adjusted tothe desired frequency by means of adjustment of the leakage resistor 03or 80.

It is also quite apparent that the back-kick, as shown by the curves ofFig. 2. is substantially exponential of the time constant equal to whereL is the inductance of the coil and R1 is the internal resistance of thetube, and, accordingly, it becomes apparent that for very highoscillation frequencies the ratio of the pulse width in the negativedirection to the pulse width in the positive direction can be consideredas ii' it were proportional to the square root of the distributedcapacity across the primary and the secondary coils divided by the valueof the effective capacity 8| which actually may be only a fraction ofthe grid capacity, due to the interaction of the grid to cathoderesistance in series with it. In this instance, the capacity 8| is ofrelatively large value, for instance, of the order of 10,000 mmf. and,on the other hand, the stray capacity is of the order of about 100 mmf.;this is found to produce the positive pulse equal to about half thewidth of the negative pulse, with the result that the increased width ofthe slots in the vertical sync signal, as shown by Fig. 1, is readilyobtained from the circuit here shown by providing the master oscillator`tube 15 with distributed winding and omitting plate tuning circuitconnections.

The blocking transformer 81 comprises two further windings 92 and 93,each of which has an output of approximately one-tenth that of theblocking oscillator, or about 20 volts (assuming a 200 volt output fromthe oscillator), with the winding 92 being in phase with the platevoltage at plate 19 of the tube 15, and the winding 93 providing anoutput of opposite phase, as shown by the curve b of Fig. 4 forinstance. The output from the winding 92 is caused to appear in thecircuits of the tubes J and L, and thus appears directly in the outputafter suitable clipping and switching. The winding 03, however, is useddirectly to synchronize the various line and keying oscillators, suchasv represented by the tubes 95 quency oscillator G and the frequencydivider H.

The second portion of the master oscillator A, represented by the tube15. comprises the section including the cathode Ill, the controlelectrode or grid |02 and the plate or anode |03. This section of thetube Vis connected as a cathode follower stage. The anode or plate |03is connected to the terminal of the winding of the transformer 81,through which positive voltage is supplied, to energize the plate oranode elements 19 and |03 of the tube. The cathode element |0| isconnected to ground potential through the cathode resistors |04 and |05.'I'he control electrode |02 connects back to receive energy, such asthat supplied by the blocking oscillator tube control electrode 18. Thesecond half of the tube 75 thus becomes effective in the operation toprevent undesired grouping of the lines in the received picture, and ifthis buer section were not present, and if the frequencydivider chainformed from tubes B, C, D and E were energized directly from theoscillating system comprising the rst half of the tube 15, it will beseen that grouping might occur which amounted to several pictureelements so as to disrupt, to some extent at least, the transmission ofthe vertical lines of the picture.

Referring next to the frequency division provided by the variousfrequency dividers, such as those represented schematically in Fig. 3and shown more particularly in Fig. 6 by the tubes B, C, D and E, itwill be seen that al1 thetubes B, C and D are of the general triodetype, such as tubes of the 6J5 type. So considered, the rst frequencydivider thus comprises the tube |05; the second frequency divider thetube |01, and the third frequency divider the tube |09.

The output energy of the second half of tube 15 is cathode coupled tothe input of the ilrst tube |05 so that tube |05 is energizedby way ofthe conductor I in accordance with the voltage drop across resistor|08.` The tube |05 comprises the usual cathode ||3, control electrode H5and thel anode or plate H1, which latter element is connected to onewinding of the transformer ||9 and also to a source of positive voltageas applied to the bonductor |2| through appropriate resistors |22 and|23, and high frequencies are by-passed to ground |24 by way of theby-pass condenser |25. The arrangement thus is similar to that by whichthe tube 15 receives its plate .or anode voltage from the conductor |2|,and similar to that in which high frequency energy is by-passed toground from the tube 15 through a similar condenser |25. A

In order to tune the period of the blocking oscillator tube |05,provision is made for the use of a grid condenser |21 and suitable gridleak elements |28 and |29, of which the latter is preferably variable inorder to provide the necessary tuning. From what was above stated, itappears that the output energy from the tube |05, corresponding to thefirst frequency divider B, is energizedat a period of 10,500 cycles,which will be assumed to correspond to one-third the frequency of themaster oscillator tube A or 15. This output energy is fed by way of thecoupling provided with the cathode resistor |3I, the coupling resistor|32 and the coupling resistor |33, which together form a couplingnetwork of the general type identified as a 1r network and consistpurely of ohmic resistances of low impedance, for instance of the orderof about ohms each. The

energy output from the first frequency divider' tube B or is thus fed tothe second frequency divider tube C or |01 in essentially the samemanner as the output from the buffer stage of the tube is applied to thetube |05.

The secondfrequency divider tube |01 comprises the usual cathode element|35, the control electrode |36 and the plate or anode |31. The plate oranode |31 connects to one winding of the transformerV |39, and alsoconnectsto the high voltage line |2| by way of resistors |22 and |23, asreferred to with regard to the tube |05.

As was explained in connection with the first frequency divider tube|05, this second frequency divider tube 01, which also may be of thegeneral type known in the art as the 6.15, is tuned by means of thecondenser |4| operating in conjunction with the resistors |42 and |43,of which the latter is preferably made variable.

The indicated connections to ground |41 are common for a great manytubes in the frequency divider and other portion of the unit.

Output energy from the second frequency di vider stage |01 is fed by wayof the resistor |49 in accordance with the voltage drop occurring acrossthe cathode coupling resistor ISI. The resistors |49 and |5l, togetherwith the resistor |53, again form a 1r section lter, as did theresistors |3|, |32 and |33 serving to couple the output of the firstfrequency divider tube |05 to the input of the second frequency dividertube |01.

At this point it might be well to point out that the 1r section filterused for coupling offers some advantages in that, by omitting thecoupling impedance it is easily possible to pre-set each stageindependently, because the subsequent connection affects the naturalfrequency but very slightly. Further, it is possible to adjust thedegree of coupling readily by changing the coupling resistor, and alsothere is no lag with this type of coupling, and, as another point, thedegree of frequency division may be counted readily since both thedriving pulses and the reduced frequency pulses appear across the outputend of the 1r'network.

The third frequency divider tube |09, which is also preferably of thegeneral type known in the art as the 6J5, serves to reduce the frequencystill further, and while the input frequency corresponding to the outputof tube |01 is assumed to be 2100 cycles, the output from the frequencyfrom the tube |09 will preferably be 420 cycles.

The tube |09 comprises the usual cathode I, the control electrode |55and the plate or anode |56 which connects to one winding of thetransformer |51. This transformer winding serves to connect high voltagefrom the conductor |2| to the plate or anode |56 by way of the resistorelements |59 and |60 at the junction of which --a condenser |6| isconnected toV by-pass any possible high frequencies to ground |24. Theother winding of the transformerv |51 is connected receive the energyoutput fromthe tube |01, and by means of the condenser element |63 andthe resistors |64 and |66, of which the latter is preferably variable.the period of the oscillator is adjusted.

In connectionwith the frequency reduction to the lower frequencies, asprovided by the tube |09, it is, however, desirable to tune the circuitincluding the grid or control electrode |55 by means of the condenser|65 which is connected in parallel to the grid coil of the transformer|51. For the higher frequency stages, such as provided |05 and |01, ithas been found that the natural capacity of the windings is generallysatisfactory to provide satisfactory perfomance. at least with theordinary way of non-distributed wind-ing, so that in other circuits thetuning condenser |65 may, as a general rule, be eliminated, although itis apparent from what is here stated that ytiming of this character maybe resorted to in any frequency' divider stage.

The output energy from the tube |09 which appears at 420 cycles, isthenfed through still another 1r section filter comprising the de-couplingcathode resistor |61 of the tube |09. the coupling resistor |69 and thegrid resistor |69 of the last frequency divider tube E or |1I. Thus tube|1| is preferably of the 6F8 type, as is the tube 15, and it uses thefirst portion thereof as a blocking oscillator section which is of aslightly unusual form in that the storage circuit is connected betweenthe cathode |12 and ground |41 and there is no storage provided in thegrid (control electrode) or plate (anode) circuits.

In this connection the energy output of the tube |09 is fed to the gridcoil of the transformer |14 and the tuning to control the duration ofplate pulse is brought about by means of the condenser |15 in a mannersomewhat similar to that explained in connection with the condenser |65of the tube |09. This condenser |15 connects, as shown, to the controlelectrode |16 of the first section of the tube |1| whose plate or anodeelement |11 connects by way of the plate coil of the transformer |14 anda pair of resistors |18 and |19 to the conductory |23, at which the highpositive potential appears by way of the connection at the terminal |80.

As was explained in connection with all of the other frequency reducingtubes, a condenser |8| connects between the resistors |18 and |19 andground |24 to by-pass any high frequencies. Output energy from the firstsection of the tube between the cathode |12 and ground |41 is of quasisaw-tooth character with a positive peak such as shown by curve d ofFig. 4. This energy is caused to appear across the cathode resistors |83and |84, of which the latter is preferably variable and used todetermine the repetition i frequency of the system, and is fed by way ofa conductor |86 to a phase control tube |90 which, for example, may beof the general type known in the art as a 6J1. The condenser |9| servesto by-pass any high frequencies to'ground.

The quasivsaw-tooth wave, as it appears in the conductor |86corresponding to the output of the first half of the tube |1|, is toserve the purpose of automatic frequency control which is provided bybeating this output with the 60 cycles per second of the power supplyfrequency which is connected at the terminals |92 and |92', and this ispossible because there is a particular linear relationship between phasedisplacement and the D. C. output in such a wave. Further, in con!nection with the tube |1|, the output from the 'plate or anode element|11 ,is preferably of a pulse nature and ls adjusted to be of a durationof approximately IIH, as was indicated by curve f of Fig. 4, and thisadjustment of the length of the pulse is, as above stated, brought aboutby tuning in the grid circuit by means of the condenser |15 in serieswith a resistor |92 and the grid coil of the transformer |14.

It was already explained that it ls desirable that this signal outputfor the plate |11 of the tube |1| shall have a duration lof slightlymore than 9H but less than |2H asthis is the character of signalrequired to operate the square wave generator `for just three cycles of3H duration, but no longer. The second portion of the tube 1|,comprising the cathode |93, the control electrode or grid |94 and theplate or anode |95 is, generally speaking, connected as a cathodefollower. It draws current which is cut off for the duration of thepulses, and thereby an inherently at top level of the key signal issecured for a time duration ofi-'approximately HH. This keying signal isdeveloped across the cathode resistor |96 and serves to operate thesecond half of the frequency divider tube 99, which is for the purposeof reducing the frequency to one-sixth that of the master oscillator 15.

Simultaneously, the plate current of the second half of this tube |1| isapplied to the relay tube 200 tomake it of a non-commutative character.This effect is obtained by feeding this output energy through theconductor 20|, so that it iiows through an appreciable portion (the part219) of the plate resistor 202 and 219 for the tube 200, and thisresults in a definite unbalance of this'relay during certainpredetermined periods and it is not vuntil the emission in the tube |1|is out o that the balance in the relay tube 200 is re-established, aswill become apparent from a further discussion of this tube in what isto follow. The effect is, however, that the relay tube 200 shall be in apredetermined and definite state with regard to operation when the rstdirectional pulse from the square wave generator and triggering tube 204reaches it, as will later be explained and as is set forth in companionapplication Serial No. 445,253, filed May 30th, 1942, which is entitledElectronic relays.

Now, referring more particularly to the automatic frequency control tube|90 which receives energy of quasi saw-tooth character on its #l grid206 from the conductor |86 by way of the time constant circuit 201comprising the parallel capacity 208 and resistance 209, it will readilybe appreciated that the impressed energy is a sawtooth voltage ofsubstantially cycles. Consequently, the amount of direct current whichthe tube |90 can pass will depend upon the instant at which the tube ismade conductive by a pulse derived from the 60 cycle power supply lineassumed to be connected to the terminals |92 and |93 being supplied tothe #2 grid 2|0 by Way of the transformer 2|| and the resistance'capacity circuit 2 I2.

Normally, the #2 grid (screen grid) of the tube |90 is negative and noplate current flows through the tube. However, during the positive swingof the power supply frequency connected to be supplied through thetransformer 2| it is apparent that the tube |90 may be made conductivefor a short instant. The necessary negative bias s uperimposed betweenthe 60 cycle per second voltage and the screen or #2 electrode 2 I0 isprovided by the resistance-capacity circuit comprising the resistance2|3 and the capacity 2 i4 which provides a self-biasing effect. It isevident that the nearer the conductor period comes to the positive peakof the #l cr control grid swing the more current will flow, asdetermined by the quasi saw-tooth applied thereto. Any A. C. componentsin the output of the tube |90 may readily be filtered in the filterchain comprising the condensers 2|S and 2|1, each connecting to ground|41 and having the smoothing resistance 2 I 0 connected therebetween sothat the resulting direct current output may be measured by means of themeter 2|9 (conventionally represented) and fed back by way of theconductor 220 through the resistor 22| to be applied to the controlelectrode 18 of the master oscillator 15 where it is caused to vary thebias on the control electrode and thereby control the operational cycle.

It is apparent that in operation the polarity of the variations shouldbe rendered such that the automatic stabilization of the frequency isobtained within a very small range of direct current, for example, onemilliampere, and this permits the control of a wider frequency variationthan ever is to be expected in practice, -even under adverse conditions.

By means ofthe variable resistors 83 (coarse) `or (fine) connected tothe control electrode 18` of the master oscillator tube 15, the directcurrent output from the tube is adjusted so as to appear atapproximately the center of the scale 4of' the meter 2 |9, so thatpositive and negative variations of the power line frequency are equallywell compensated. Any high frequencies induced into the secondarywinding of the transformer 2| are readily by-passed to ground by meansof the bypass condenser 222.

The tubes 99, 204 and 200 respectively serve to provide the necessarysquare wave bias so as to obtain equalizing and frame signal clippingwithin a mixer tube 225 (also preferably of the general type known as a6.17) which will be later explained in further detail. Ihe tube 99 isarranged to function as a frequency divider tube and is essentially forthe purpose of providing a frequency output corresponding to one-sixththe frequency of the master oscillator 15. o In its broadest aspect, thetube 99 is connected in the same manner as was disclosed for thefrequency divider unit set forth and claimed in my co-pendingapplication Serial No. 433,289, filed March 4, 1942, entitled Frequencydivider (RCA Docket 21,107). Energy to drive the frequency divider unit99 is derived from the coil 93 associated with the transformer winding81, and the wave energy (as shown by curve Fig. 4b for example) inducedinto this coil is then fed by way of a time constant circuit comprisingthe parallel combination of resistor 221 and condenser 228 to thecontrol electrode 229 of tube 99.

The time constant of the resistance capacity circuit 221-228 isessentially such that operation takes place at approximately one-sixththe frequency of the master oscillator 15 and, as was above explained,when the energy from the tube 15 is fed to the control electrode 229 ofthe tube 99 it is supplied in inverted polarity, as was indicathed forinstance by curve b of Fig. 4. It is apparent that the inversion ofpolarity, in effect, gains time so that the switching mechanism is readyto supply the required bias on the mixer tube 225 prior to the time therst equalizer pulse is applied by way of the condenser 23 I'.

The frequency divider tube 99 is operated in a start-stop manner, andthe bias on the control electrode 232 of the second half of the tube ismade highly positive as long as the plate current in the second half ofthe tube |1| is not interrupted. 'I'he cathode output of the tube 1| asit appears across the resistor 96, is supplied to the control electrode232 by way of the conductor 233, but the cathode element 234 of tube 99,acting as a cathode follower stage, is biased highly positive,

and the plate current iiowing in the rst half of 'of picture scanning-corresponding to the time tion HH, as shown by curve f of Fig. 4, thegrid.

bias applied to the control grid 232 of the second haii' of the tube 99is reduced and the cathode 234 follows. Consequently, the rst half ofthe tube 99 comprising the cathode 234, the control electrode 229 andthe anode or plate 235 comes into action as a frequency divider andprovides an output at a frequency of one-sixth the frequency of themaster oscillator, or at 5250 cycles, at the conductor 236 and acrossthe resistor 231. Consequently, it is apparent that a series of fourpositive pulses with intermissions of a period 3H will appear across theresistor 238 connected to the anode or plate 239 of the second half ofthe tube 99, and it is further apparent that no more than four suchpulses can be produced because, in the period between 9H and 2H (seeFig. 4. curve f) the plate current in the second half of the tube |1| isrestored and the action of the tube 99 thereby ended.

In companion application Serial No. 445,253, led May 30, 1942, entitledElectronic relays, it has been explained how square waves may beproduced by two triodes in vspecial connection, as shown by the tubes204 and 200 under the inhuence of positive triggering pulses.

The arrangement of Fig. 4 of the last mentioned specication, showedgenerally an arrangement closely related to that embodied in the useofthe tube 204 as the driver tube or the square wave generator triggertube, and the tube 200 as the relay tube and ampliiler tube. It is,however, to be noted that in contrast to the arrangement shown by thelast mentioned co-pending application, a tube of the general type knownin the art as the 6F8 (with separate cathodes) is substituted for theform of relay tube previously shown, so that adequate power output maybe de-` livered for the action of the mixer channel including the tubes225 and 226 by cathode-follower coupling. i

Output energy from the frequency divider unit or tube 99 is fed to thecontrol electrodes 24| and 242 of the driver tube 204 by way of thecoupling condensers 243 and 244 respectively. This tube has its cathodeelement 246 appropriately biased relative to ground 241 by meansl of abias resistor 248 in accordance with potential supplied by the resistor249 from the positive potential conductor 250 which also supplies platevoltage for the plate or anode elements 235 and 239 of the tube 99through the resistor 25| The control electrodes 24| and 242 of thedriver tube are connected with the control electrodes 253 and 254 of therelay tube 258, so that the condenser 243 and the resistor 255 form onetime constant cirouit and the condenser 244 and the resistor 256 formthe second time constant cir.- cuit, both time constants being the same.

The cathode elements 251 and 258 of thevtube 20|) obtain bias relativeto ground 241 by way of resistors 259 and 260 connecting through acommon resistor 26| to ground, with a condenser 262 by-passing highfrequencies to ground around the resistor 26|. Output energy from therst half of the relay tube 200 flows from the plate or anode 263 thereofby way of the conductors 265 and 261 and the coupling condensers 268 and269 to the relay tubes 21| and 212 (or P and K) respectively. Also fromthe cathode 258 of the second half of the relay tube 280 output energyis derived :ln accordance with the Voltage drop across the cathoderesistor 260, and this output, as before stated in the discussion ofFig. 3, flows through the coil 92 and the coupling condenser 23| to thecontrol electrode 213 of the mixer tube 225, so that at the controlelectrode 213'voltage .waves corresponding to the curve a of Fig. 2 (thefrequency output of the master oscillator starting with negativepolarity) and curve h of Fig. 4 are combined. A leak resistor 214connects the control electrode 213 to the cathode 215 of Athe mixer tube225, and the cathode 215 is biased relative to ground 241 by the biasingresistor 211.

, level Will be as indicated by the line E in Fig. 2a.

In connection with the square wave generator units 204 and 200, it wasabove pointed out that under normal circumstances it might be possiblefor the tube 200 to become conducting, so that one or the other of thetwo halves of the tube would draw current when the first trigger pulsearrives. However, for the purpose of developing a synchronizing signalgenerator arrangement, it is essential that it be determined which ofthe two halves of the relay tube 200 vshall conduct, and, to this end,an unbalanced condition is provided by causing the output current fromthe second half of the tube |1| to flow through a portion 219 of theplate resistors 202 and 219 of the second half of the tube 200, Once thecurrent flowing through the second half of the tube |1| is cut off, therelay tube 200 is balanced, in that the plate resistor 280 for the rsthalf of the tube is made equal to the series resistance provided by' theseries combination of the resistors 202 and 219.

It thus becomes apparent that the relay tube 200 will always start inoperation with the second half, comprising the cathode 258, the controlelectrode 253 and the plate or anode 28| conducting, and in this way thecurve h of Fig. 4 is obtained in such a way that there is provided anoutput pulse which is symmetrically positioned about the axis with no D.C. component, in' contrast to the normally expected D. C. componentwhich would ordinarily appear with D. C. coupling.

Reference now may be made to the mixer tubes 226 and 283 which each havetheir #l grid or control electrodes 285 and 281 respectively connectedto the output electrode 289 and the plate resistor 290 of the secondhalf of the line frequency oscillator tube 95. Thus, connections aremade to the mixer tube 226 via the conductors 29| and 292 and thecoupling condenser 293, anf' to the blanking tube mixer 283 by way ofthe conductor 29|, the resistor 294 (used to drop the voltage) and thecoupling condenser 295.

The grid leak resistor 296 is connected between the control electrode285 and the cathode 291 of the mixer tube 226, and likewise the leakresistor 298 is connected between the grid or control electrode 281 andthe cathode 299 of the mixer tube 283, and each of these resistors is ofrelatively high value. In. each case, automatic grid bias of such amagnitude is built up in the tubes that only the positive peaks of theline frequency impulses, forming the output from the tube 95, areampliiied in the super sync mixer tube 226.

ammassol i The blanking tube mixer 233, however, hasincluded between theconductor 29| and the coupling condenser 295, through which the outputof the tube 95 is supplied, the series resistor 294 hereinabovementioned which serves to limit the grid current and consequentlyresults in a clipping action taking place within the tube 263 at a lowerlevel. This, of course, results then in the production of a longerduration pulse from the i tube 283 than is obtained from the tube 226 aswould be expected from the showings of curves e, f and y respectively ofFig. 2. which diagrammatically illustrate the production of the lineblanking and the synchronizing pulses from the common pre-shaped inputsignal.

Suitable positive voltage for the mixer tubes 225 and 226 is supplied tothe plate or anode elements 300 and 30| thereof by way of the highvoltage conductor 250 and the resistors 303 and 304 with the condenser305 serving to by-pass any high frequencies to ground 241. Similarly,the line frequency oscillator tube 95 and the relay tube 212 each derivepositive plate potential by way of the conductor 301 connecting with theconductor 250 and the plate resistors, as indicated, so that platepotential is supplied to the first half of the tube 95 by way of theresistors 308 and 309 with the by-pass of high frequencies to ground 241being provided by the condenser 3|0, and plate potential to the secondhalf of the tube 95 is then provided by the plate resistors 308 and 290hereinabove mentioned. Likewise, plate potential for the anode or plateelement of the relay tube 212 is provided from the .conductor 301 by wayof the resistor 3|| and the resistor 3|2 for the rst half of the tube,and the resistor 3|3 for "the second half of the tube.

`The general circuit arrangement of the single pulse relays 59 and 69 ofFig. 3 are shown more particularly by the tubes 212 and 21| andassociated circuits respectively, used to control the operation of themixing tubes 225 and 226 as well as the shaping amplifier 3|1 later tobe described.

' Further, the single pulse relay arrangement shown particularly by thetubes 212 and 21| respectively, and their associated circuit elementsform the subject matter of a separate co-pending application identifiedas Single pulse relay, filed July 30, 1942, Serial No. 452,922.

In some senses the relay arranement 212 (and consequently also the relay21|) tends to func* tion as a multi-vibrator, but is of a somewhatdiierent form than the well known multi-vibrator in that it is of thetype which may be stated to be A. C.D. C. coupled.

'I'he second half of the single pulse relay tube 212, which includes thecathode 3|9, the control electrode 32| and the plate or anode element323 is A. C. coupled through the condenser 325 and the bleeder resistorcombination comprising the resistors 326 and 321, so that the 'energyfrom the second half of the tube is fed back to the control electrode329 of the first half of the tube which includes also the plate or anodeelement with a connection being made from the controlelectrode 32| andthe junction of the resistor 334 to ground byway of the resistor element335.

The general arrangement of the system thus disclosed is one whichoperates in such a manner that lt can develop but one output pulse at atime, and the duration of the operational cycle may -be readilycontrolled by the pre-arranged time constant determined by the capacity325 and the sum of the resistor values of the resistors 326 and 321, aswell as the general tube constants. If there are no triggering impulsesapplied to the system by way of the conductor 261 connecting to theoutput of the relay tube- 200 and supplying energy by way of thecondenser 269 (which is quite small), the relay arrangement ismaintained in a state where the left hand half of the relay tube 212 isconduct'- ing and the second half of the tube is blocked 01T because thegrid or control electrode 329 is connected to the cathode 3|9 across theresistor 321. Consequently, the output pulse will be noncommutative. l

If reference is now made, however.l to the curves of Fig. 5, and firstto curve a thereof, it will -be seen that the relay device may betriggered by the arrival of a pulse of negative polarity, such as thatshown by the rst pulse, reading from leit to right, in curve a of Fig.5. Normally, the relay tube 212 would trigger in the opposite directionby the arrival of the second pulse shown b'y second curve a of Fig. 5,Wluch second pulse is of positive polarity, under conditions where thetime constant of the operation was of a time order comparable to the innis no energy feedback terruption period -between pulses. However,provision can be made whereby the relay tube 212 will not follow thefirst positive pulse received subsequent to the receipt of the operationinitiating negative pulse, but rather the relay will be triggered in theopposite sense by the arrival of the second positive pulse following thecontrolling negative pulse and this delay can readily be established bylengthening the time constant provided by the system to a valueapproximately twice as long as the rst and second the time vbetween therst negative and the rst positive pulse.

If these conditions are followed, then the relay will switch back to itsnormal state (that is, the second half non-conducting and the rst halfconducting) upon the arrival of the second positive pulse (as in curve aof Fig. 5), following the operation initiating negative pulses, and forthis purpose the time constant of the relay tube arrangement 212 is madeto coincide with a time period of operation of the order of 9H (see Fig.

The relay tube 21| is of the same general nature as the relay 212 and,in its normal state, the second half of the tube, comprising the cathode339, the control electrode or grid 340 and the plate or anode 34|, doesnot pass current, so that there -by way of the condenser 343 and theresistor elements 344 and 345, at the junction of which resistorelementsthe control electrode 346 of the rst half of the tube is connected, asindicated.

The plate or anode 341 of the iirst half of the tube connects back tothe control electrode or grid 340 of the second half of the tube by wayof the D. C. coupling resistor 349 and tofground 241 by way of theresistor element 350, as was shown for tube 212. Also, as was the casewith the relay tube 212, a common cathode bias, relative to ground 241,for both halves of the tube is provided by the cathode resistor 35|which, if desired, may be by-passed for high frequencies by thecapacitor 352.

The relay tube 21| essentially is intended tol act as a frame blankingcommutator and, accordingly, the time constant is so chosen that its'period of operation, as determined by the capacity 343 and the sum ofthe resistors 344 and 345, should be longer than for the relay 212 andpreferably of a time period of the order of about |2H, so that thecondenser 343 is usually somewhat larger than the condenser 325 of therelay tube 212.

In order that the relay tube 21| shall not operate to render the rsthalf non-conducting upon the arrival of the second positive pulse (suchas that shown by curve a of Fig. 5) but at a subsequent pulse, it isunderstood, of course, that the relay tube 21| is controlled from thesame source provided by the tube 200 as is the relay tube 212.

Wave forms of the cathode and plate ouputs of the single puise relays212 and 21| are generally shown by curves b, c and d respectively ofFig. 5, and from these pulse indications it will be seen that the syncpulses are not flat topped but nevertheless show a linear increase anddecrease respectively in amplitude plotted against time. This is due tothe interaction of the two plate currents owing in the tubes 212 or 21|through the common cathode resistors 332 and 35| and acting in oppositesenses thereupon.

In order to obtain a pulse output of desired wave form and height, theplate and cathode pulses may be mixed in a common resistive net- Workwhich is provided by means of the resistors 353 and 354 for the firsthalf of the relay tube 212, and the resistors 355 and 356 for the secondplate circuit of the same tube, so that the output from the first halfof the tube, as it appears in the conductor 351, shall coincideapproximately with the wave form e1 of. Fig. 5, and the output energy asappearing in the conductor 358 shall be approximately of the wave formas shown in e2 of Fig. 5, by selecting the appropriate and criticaltapping point across the respective bleeder resistors last named. Inthis way, the pulse output from the first half of the relay tube 212, asit appears in the conductor 351, is always positive in sign, and thepulse output from the second half of the tube 212, as it appears in theconductor 359, is always negative in sign.

By appropriate selection of voltage for the plate supply of the tubes21| and 212 at a value of the order of about 200 volts, both of theseoutputs may be made of approximately 50 volts by an appropriate choiceof circuit constants.

The arrangement of the relay tube 21| is approximately the same as thatdisclosed for the tube 212, except that the output energy from thesecond half of the tube, as it appears in the coinductor 36|, is ofnegative sign, and, like the arrangement of the relay 212, the tubefunctions to produce relay action of a. predetermined time duration inresponse to input voltages which exceed a predetermined value, or to thereceipt of input pulses.

Reference now may` be made to the line frequency oscillator tube 95which is connected to receive energy at a frequency of the masteroscillator tube as such energy is picked up in the coil 93 associated asan independent winding upon the main oscillator transformer 81. Thepulse of energy as it appears in the winding 93, and as it is fed by wayof the conductor'363 to control the control electrode 365 by way of theassenso coupling condenser 363 is initially of positive polarity, asshown for instance by curve b of rig. 4.

The general arrangement of the line frequencyA oscillator tube issubstantially like that disclosed and claimed in my co-pendingapplication Serial No. 433,289, led March 4, 1942., where reference maybe made particularly to Fig. 2 thereof, for instance. In the arrangementherein disclosed, the ilrst half Yof the tube 95 comprising the cathode351, the control electrode 365 and the plate or anode 359 feeds itsenergy by way of the potential divider provided by the resistors 359 and319 so as to supply energy to the control electrode 31| of the secondhalf of the tube 95.

-The cathode 361 is appropriately biased to ground 241 by way of thecathode resistor 313 and the second half of the tube 95, as wasexplained in the last referred to co-pending application, acts as acathode follower stage so that through the appropriate choice of thetime constant and the tube operation as weil as the circuit elementsprovided by the condenser 366 and the leak resistor 315, the tube 95 maybe caused to produce a pulse output from the plate or anode 239 of thesecond half thereof which will appear in the output conductor 29| inpositive sign, so as to be applied by way of the coupling condenser 293to energize the control electrode 285 of the mixer tube 226.A This samemixer tube 226 has energy pulses of negative polarity (like pulses ofcurve e2 of Fig. 5) supplied to the #3 grid 316 through the couplingcondenser 311.

The output pulsesA from the relay tube' 212, which are of positive signas shown by curve e of Fig. 5, and which appear in the conductor 351.are applied directly to the #3 grid 319 of the mixer tube 225. Thus, itcan be seen that with the mixer tubes 225 and 226 connected togetherwith a common plate supply and a common plate output circuit, outputenergy can be fed to the shaping amplifier tube 390 across the resistor39|, so that this energy is then applied between the #l grid 392 andground 241. The cathode 394 of thetube 399 is appropriately biasedrelative to ground 241 bythe bias resistor 395 and any high frequenciesmay be by-passed, as desired, by the by-pass condenser 396.

It is, of course, apparent that the circuit parameters of the tubes 225and 226 may be adjusted in such a way that the energy wave form appliedtov the grid or control electrode 392 of the shaping amplifier tube390is'of the general wave form corresponding to that diagrammaticallyrepresented, for instance, by curve m oi Fig. 4 (only with "round"edges), and this is determined, in turn, by the relative polarity of theenergy impressed upon the #l and #3 grids of the mixer tubes 225 and 226which is caused to appear in the wave form fed through the resistor39|.4

The operation of the wave shaping amplifier tube 390 which, forinstance, may be of the general type known in the art as the GAC?, issuch as to increase the steepness of the leading and trailing edges ofthe pulses applied thereto, anc' will be further explained in connectionwith a discussion of the wave shaping tube 3|1, which is also preferablyof the same general type as the tube 390.

The output energy from the second half of thi relay tube 21| issupplied, as above stated, by way of the conductorv 36| and the couplingcondenser 398 to the #3 grid 399 of the shaping amplier 311, so thatthis energy appears across the resistor 40| and is applied between the#3 grid 399 and the tube cathode 402, which latter element is biasedrelative to ground 241 by the cathode bias resistor 403. Similarly, theoutput from the blanking tube mixer 283, as it appears in the platecircuit of this tube and in the conductor 405, is supplied to the #lgrid 401 by way of the time constant circuit comprising the resistor 403and the capacity 09 and caused toappear across the leak resistor 410connected between the #l grid 301 and ground 261. Thus, output energypulses from the relay tube 211, which are ot a duration approximately12H, as shown by curve n of Fig. 4, are applied in the negative sense tothe #3 grid 399 of the shaping amplifier tube 311 and the output energypulses from the blanking mixer 283 are applied simultaneously to the #lgrid 301 of the shaping amplifier tube 311.

Referring back now to the relay tubes 212 and 21 1, it will beappreciated that With the first half of each tube normally conductingprior to the receipt of the triggering pulses as shown, for instance, bycurve a of Fig. 5, the potential appearing in conductor 351 and appliedto the y:r3 grid of the tube 225 is negative with respect to thepotential which this grid will assume when. the first half of the tube212 ceases to draw current as of the time when the iirst negative pulseis impressed upon the control electrode 329 by way of the couplingcondenser 269.

Likewise, the #3 grid 31E of the tube 226 is normally held at thepotential of its cathode 291 by virtue of the connection thereto throughthe grid leak resistor 313, and then when the relay 212 is triggered sothat current ows through the second half of the tube including the plateor anode 323, the control electrode 32| and the cathode 319, a negativeimpulse such as shown by curve ez is fed by way of conductor 358.

The signals appearing in the output of the second half of the tube 21|are, as above stated, of the same general character as the outputsignals of the second half of the tube 212, and, accordingly, the tube21| is arranged to control and operate the shaping amplifier 311 byvirtue of the impulse applied through the condenser 398 to the controlelectrode 399.

In order that the mixer tubes L and M and Q and their associated shapingampliers N and R may be properly operated to derive the desired form ofsignal pulse, the time constant of the relay tube 212 is made of theorder of 9H while for the relay tube 21| this time constant islengthened to the order of 12H,` although therelay tube 21| iscontrolled from the same source as the relay 212, but by lengthening thetime constant the relay 21| will not operate as does the relay 212 uponreceipt of the second positive pulse, as shown by curve a of Fig. 5, butwill change its state of operation in accordance with the adjustment andsize of the condenser 343. After the sync signals and the blankingsignals have been mixed in their respective channels, and as they appearindividually across the load resistors 304 of the tubes 225y and 223 andthe load resistor of the type known in the art as the 1852 or the asdesired. It thus becomes apparent that across 415 of the tube 283, thesignals are then red into high gain tubes, such as the shaping ampliers390 and 311 respectively for the sync and the blanking signals.

As was above pointed out, the amplifiers 390 and 311 areprimarily forincreasing the steepness of the leading and trailing edges of the signalpulses applied thereto, and this is readily done by using a high gaintube, for instance, one

the plate resistor -415 of the tube 283 only the line blanking. signalsappear, as the complete' blank- -ing sequence has not been provided upto this point of the circuit. The addition of the frame blankingimpulses is provided by the use of the rst blanking-shaping amplifiertube 311 which is used in a sense as a modulator by applying theblanking impulses upon the #3 grid 399.

Referring now more particularly to the sync signal channel, the outputsignals from the mixer tubes 225 and 226 are applied through the circuitcomprising the parallel combination of the resistor 915 and condenser M1so as to be impressed upon the control electrode 392. The parallelcombination of the' resistor. 415 and the condenser 311 acts, ingenerates a low frequency compensator and corrects the iniiuence of theplate lter combination comprising the resistor 3113 and the condenser305 which becomes slightly charged during the frame impulses. Generallyspeaking, the eiiect of this low frequency emphasis is cancelled whenthe circuit comprising the resistance 415 and the condenser 411 is sodesigned that it has a time constant substantially equal to that of theplate filter combination of the tube. ,1n addition, the arrangementprovides means by which positive bias may be applied to the grid orcontrol electrode 352 of the tube 39d, and this has some advantageouseect in reducing ripple and hum underlying the basis of the pulsesequence introduced by the plate supply to the tubes 225 and 216. Outputenergy from the tube 39u is then fed by way or' the conductor 419 andcoupling condenser 42| so as to be impressed upon tne ampliiier tube 425which is provided with the usual leak resistor 421. 'lhe shapingampiiiier tube 3911 is adapted to emphasize the high Irequencies byreason oi' the capacity 39u' being arranged to shunt the degenerativecathode resistor 395. 'lhe tube 42e is coupled to receive the outputfrom the shaping tube 39u. For this purpose, the signal output from thetube 39u is red from the plate -429 through the conductor 419 of thecoupling condenser 1121 to be 'impressed upon the control electrode 431of the tune 425, and then appears in the output circuit of this tubeacross the output-resistor 433. 'lhe tube 325 is primarily for thepurpose of providing power and polarity inversion. The tube 425 deliverspositive super sync by cathode follower action across its cathoderesistor 453, and simultaneously delivers negative super sync of equalamplitude across its plate or output resistor 433. Each, however,represents a slightly higher impedance and makes a separate matchingtube orten desirable, if it is desired to connect this output upon a lowimpedance line.

With` regard to the blanking signals as amplied in the shaping amplier311, it will be noted that the degenerative en'ect of the cathoderesistor 433 is substantially overcome through the inciusion of aby-pass condenser 635 similar to the condenser 316 used with the tube391) to by-pass its cathode resistor. c

For the purpose of improving the high frequency response in the shapingamplifier 311, a peaking coil 431 is included in the plate circuit, andthe output from the tube 311 is then fed across the load resistor 439through the conductor 441 and coupling condenser 442 to be impressedupon the control electrode 443 of the output blanking amplifier tube445. The output blanking amplifier 445, like the output sync amplifier425, is also preferably of a reasonably high gain typetube and functionsin a manner quite related to the tube 425 just diSCuSSed and might bedescribed as a power matching tube.

Signal energy. output from the tube 445 is derived from the plate oranode element 441 across the load resistor 448 and also across thecathode resistor 449 which serves to bias the cathode 450 relative toground. A similar bias is applied to the cathode 45| of the tube 425 byway of the cathode resistor 453.

In order that either positive or negative synchronizing and blankingpulses may be derived from the blanking output amplifier 445 and thesync amplifier 425, suitable terminal points 460 and 462 are providedfor the tubes 445 respectively to obtain negative polarity blanking andsync signals, and terminal points 464 and 466 are provided respectivelyfor obtaining the positive polarity signals which, as is apparent, areobtained across the cathode output resistors 449 and 453 respectively.

Under these circumstances, the ends of the conductors 461 and 468respectively may be connected on the one hand to terminals 469 and 462for cases where the negative blanking and sync signals` are desired, or,as indicated by the dotted line, the connection between the ends of thecong ductors 461 and 468 to the terminal points 464 and 466respectively. Where it is desired that the blanking and sync pulses beof a positive polarity, connections may be made by the terminal points464 and 466, so that the'outputs supplied to these conductors are takenrespectively across the cathode output resistors 449 and 453 of theoutput blanling and output sync amplier tubes 445 and 425 respectively.These signals are then fed through the loading resistors. 41| and 413 tobe supplied from the terminal point 415, at which point it is apparentthat there is a superposition of both the blanking and the sync pulsesso that there is obtainable at the terminal pointA 415 a pedestal signalwith adjustable super sync pulse combined.

Power for operating the complete system is derived by way of thetransformer 41.1, for instance, whose primary winding 418 is connectedto terminal points 419 and 489 which are, in turn, con` nected to asuitable source of power supply energy not shown. The secondary winding46| of the transformer 411 is connected in known manner to the plateelements 482 and 482' of the full wave rectifier tube 483. The midpointof the transformer secondary 46| isconnected to ground 241 in knownmanner.

Suitable smoothing is provided by way of the shunt condensers 485, 485and 481' and the series resistors 488 and 439 which QOnnect to thepositive or cathode terminal 490 of the rectier tube. For the purpose ofprovidin`g`,\further stabilization of the output voltage from*k thesystem, a pair of series connected voltage regulator lamps 492 and 493is provided in well known manner.

It can be appreciated, from the connections shown, that the positivevoltage for the various tubes of the system is derived from the positivevoltage conductors 495 and 496 respectively which are arranged toconnect with the various conductors indicated as supplying voltage tothe various tubes of the arrangement and also to the terminal pointssuch as |80, which connection is not shown in detail for the sake ofsimplicity ofl showing. In this connection, it may be pointed out that aregulated power supply is generally required for the timing andcorrecting circuits only, but, as a general rule, not for shaping andpower amplifiers.

What I claim is:

1. A television synchronizing signal generator comprising a masteroscillator for generating steep front asymmetric impulse energy waves ofa predetermined frequency and impulse duration, clipping means forderiving each of a plurality of separate energy waves from the masteroscillator by clipping at predetermined separate amplitude levels of theimpulse energy waves, frequency reducing means to derive energy from themaster oscillator at a sub-harmonic thereof, clipping means for derivingfrom the reduced frequency waves energy at each of a plurality ofpredetermined energy levels, and means to combine the Several producedenergy Waves.

2. A synchronizing signalfgenerator for interlaced television comprisinga master oscillator for generating steep front asymmetric impulse energyWaves of a predetermined frequency and impulse duration, clipping meansfor deriving equalizing and frame synchronizing energy waves from themaster by clipping the asymmetric energy output waves at predeterminedseparate amplitude levels, means to develop a phase-advanced energy wavefrom the master oscillator output, frequency reducing means to developline frequency synchronizing signals, means to control said frequencyreducing means by said phase-advanced energy wave to derive energy underthe control of the master oscillator at a sub-harmonic frequencythereofl clipping means for deriving from the reduced frequency wavesenergy at each of a plurality of predetermined energy levels of the saidwave, and a combining circuit to combine the several developed signals.

3. A synchronizing signal generator for interlaced television comprisinga master oscillator for generating steep front asymmetric impulse energywaves of a predetermined frequency and impulse duration, clipping meansfor deriving each of a plurality of separate enrgy waves from the masteroscillator output by clipping said output energy Waves at predeterminedseparate amplitude levels, means for deriving a phase-advanced energywave from the master oscillator output, frequency reducing means, meansto energize the frequency reducing means under the control of thephase-advanced energy wave to derive energy at a sub-harmonic frequencyof the master oscillator, clipping means for deriving from the reducedfrequency Waves energy at each of a plurality of predetermined energylevels of the said waves, and means to combine the several producedenergy Waves.

4. A television synchronizing signal generator comprising a masteroscillator for generating steep front asymmetric impulse energy Waves ofa predetermined frequency and impulse durationA with predetermined widthin positive and negative portions of the cycle, clipping means forderiving each of a plurality of separate energy waves from the master byclipping at predetermined separate amplitude levels of the impulseenergy waves, frequency reducing means to derive energy from the masteroscillator at a subliarmonic thereof, clipping means forderiviug fromthe reduced frequency waves energy at each of a plurality ofpredetermined energy levels, and mixer means operating under the controlof the master oscillator to combine the several energy waves developed.

